<!DOCTYPE html>
<html lang="zh_CN">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box{
            width: 100px;
            height: 100px;

            background-color: red;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>